Tip the flour and salt into a bowl and rub the butter into them. Stir in the sugar and lemon rind. Mix the ingredients until they start to bind together to form a dough.
Shape the dough into a cylinder shape, about 6-7cm in diameter, and cut into rounds about 1cm thick. Place them on the lined baking sheet.
Bake for 10-15 mins, or until they start to turn lightly golden. Remove from the oven and leave them to cool on the baking sheet for a few mins. Transfer to a wire rack to cool completely.
Notes
For extra sweet shortbread, try removing the lemon zest and adding a handful of your favourite chocolate chips.